Karl Crailsheim

Nutrition and health in honey bees.

Adequate nutrition supports the development of healthy honey bee colonies. We give an overview of the nutritional demands of honey bee workers at three levels: (1) colony nutrition with the possibility of supplementation of carbohydrates and proteins; (2) adult nutrition and (3) larval nutrition. Larvae are especially dependant on protein and brood production is strongly affected by shortages of this nutrient. The number of larvae reared may be reduced to maintain the quality of remaining offspring. The quality of developing workers also suffers under conditions of larval starvation, leading to slightly affected workers. Larval starvation, alone or in combination with other stressors, can weaken colonies. The potential of different diets to meet nutritional requirements or to improve survival or brood production is outlined. We discuss nutrition-related risks to honey bee colonies such as starvation, monocultures, genetically modified crops and pesticides in pollen and nectar.ZusammenfassungEine ausgewogene Ernährung mit ausreichend Proteinen, Kohlenhydraten, Fetten, Vitaminen und Mineralstoffen ist notwendig für das Überleben eines Bienenvolkes, die Entwicklung der Arbeiterinnen und die Aufzucht von Brut. Im Superorganismus Honigbiene sind diese drei Ebenen der Ernährung eng miteinander verknüpft (Abb. 1), und Defizite in einer dieser Ebenen wirken sich negativ auf die anderen aus.Für das Überleben des Volkes sind vor allem Kohlenhydrate notwendig. Eine Arbeiterin benötigt pro Tag etwa 4 mg verwertbaren Zucker. Allerdings sind nicht alle Zucker verwertbar, einige sind für Bienen giftig. Ebenfalls giftig ist Hydroxymethylfurfural (HMF) das sich bei thermischer Zersetzung und langer Lagerung aus Zuckern bildet. Der HMF Gehalt erhältlicher Maissirupe liegt zwischen 3,1 und 28,7 ppm, kann aber durch Lagerung bei zu hohen Temperaturen drastisch ansteigen und die Mortalität von Bienen erhöhen.Pollen ist die natürliche Proteinquelle von Bienen. Daraus bilden Ammenbienen ein proteinreiches Futter für die Brut. Ist nicht genügend Pollen vorhanden, reduziert das Bienenvolk die Zahl der produzierten Larven durch Kannibalismus. Ein Mangel von Protein in der Larval-oder Adultnahrung führt zur reduzierten Entwicklung der Brutfutterdrüsen und Ovarien sowie einer kürzeren Lebensdauer. Proteinmangel während der Larvalernährung führt darüber hinaus zu beeinträchtigter Thoraxentwicklung, Flugleistung und Verhaltensänderungen. Bei Pollenmangel können dem Bienenvolk andere Proteinquellen angeboten werden, Tabelle I zeigt die pro Tag konsumierten Mengen unterschiedlicher Diäten, deren Bestandteile, Proteingehalt und die Größe der untersuchten Einheit. Ein Proteingehalt zwischen 23 und 30 % hat sich als zur Brutaufzucht geeignet erwiesen. Unseren Berechnungen zufolge erhält ein Volk mit jedem konsumierten Gramm etwa die Menge Protein die 4 Larven bis zur Verdeckelung benötigen.Pollen liefert ebenfalls Fette, die vor allem in der Larvalentwicklung benötigt werden. Honigbienen können Sterole nicht selbst herstellen, und verfüttern überwiegend 24-Methylen-Cholesterin an die Brut. Das tun sie, unter Verwendung von Körperreserven auch dann, wenn kein Cholesterin in der Nahrung vorhanden ist.Arbeiterinnen (oder symbiontische Mikroorganismen) sind in der Lage Vitamin C zu synthetisieren. Pyridoxin, ein Vitamin aus dem B-Komplex, ist hingegen notwendig für erfolgreiche Brutaufzucht. Obwohl fettlösliche Vitamine nicht essentiell für die Honigbiene sind, steigert ihre Anwesenheit in der Diät die Menge an produzierter Brut.Neben dem Verhungern oder der erwähnten Mangelernährung stellen einseitige Ernährung durch Monokulturen, genetisch modifizierte Pflanzen oder vom Menschen oder der Pflanze produzierte Giftstoffe die mit der Nahrung eingetragen werden Gefahren für die Honigbiene dar.

Managed honey bee colony losses in Canada, China, Europe, Israel and Turkey, for the winters of 2008–9 and 2009–10

Summary In 2008 the COLOSS network was formed by honey bee experts from Europe and the USA. The primary objectives set by this scientific network were to explain and to prevent large scale losses of honey bee (Apis mellifera) colonies. In June 2008 COLOSS obtained four years support from the European Union from COST and was designated as COST Action FA0803—COLOSS (Prevention of honey bee Colony Losses). To enable the comparison of loss data between participating countries, a standardized COLOSS questionnaire was developed. Using this questionnaire information on honey bee losses has been collected over two years. Survey data presented in this study were gathered in 2009 from 12 countries and in 2010 from 24 countries. Mean honey bee losses in Europe varied widely, between 7–22% over the 2008–9 winter and between 7–30% over the 2009–10 winter. An important finding is that for all countries which participated in 2008–9, winter losses in 2009–10 were found to be substantially higher. In 2009–10, winter losses in South East Europe were at such a low level that the factors causing the losses in other parts of Europe were absent, or at a level which did not affect colony survival. The five provinces of China, which were included in 2009–10, showed very low mean (4%) A. mellifera winter losses. In six Canadian provinces, mean winter losses in 2010 varied between 16–25%, losses in Nova Scotia (40%) being exceptionally high. In most countries and in both monitoring years, hobbyist beekeepers (1–50 colonies) experienced higher losses than practitioners with intermediate beekeeping operations (51–500 colonies). This relationship between scale of beekeeping and extent of losses effect was also observed in 2009–10, but was less pronounced. In Belgium, Italy, the Netherlands and Poland, 2008–9 mean winter losses for beekeepers who reported ‘disappeared’ colonies were significantly higher compared to mean winter losses of beekeepers who did not report ‘disappeared’ colonies. Mean 2008–9 winter losses for those beekeepers in the Netherlands who reported symptoms similar to “Colony Collapse Disorder” (CCD), namely: 1. no dead bees in or surrounding the hive while; 2. capped brood was present, were significantly higher than mean winter losses for those beekeepers who reported ‘disappeared’ colonies without the presence of capped brood in the empty hives. In the winter of 2009–10 in the majority of participating countries, beekeepers who reported ‘disappeared’ colonies experienced higher winter losses compared with beekeepers, who experienced winter losses but did not report ‘disappeared’ colonies.

Physiology of protein digestion in the midgut of the honeybee (Apis mellifera L.)

Abstract Proteolytic activity in the midguts of pupae and imagos of worker honeybees was determined over a 1-yr period. The bees were of defined ages and the size of the hypopharyngeal glands was used as a parameter of their functional status. The activities of trypsin-like, chymotrypsin-like enzymes and the total caseinolytic activity were investigated; they did not depend on Ca 2+ and showed optimal turnover at pH values above 7. Proteolytic activity is limited in pupae and newly emerged bees, then increases rapidly in the first hours of the imago stage. Proteolytic activity and the relation between trypsin- and chymotrypsin-like activity vary with age, season and functional status of the insects. Nurse bees show the greatest proteolytic activity. Age-dependent distributions of enzymatic activities in the endo- and ecto-peritrophic space indicate that the peritrophic membrane establishes compartments within the midgut lumen.

The flow of jelly within a honeybee colony

SummaryThe flow of jelly from 100 nurse bees to the members of two normal-sized colonies was measured during one night. To follow the flow, nurses were injected with 14C-phenylalanine. They incorporated this label into the protein of their hypopharyngeal (brood food) glands and their own body protein. When they were allowed trophallactic contacts during the investigation period a loss of label and a shift away from the abdomen was observed, indicating protein synthesis in the hypopharyngeal glands from previously stored protein. Very young larvae were fed less frequently than older ones. Younger workers received larger amounts of jelly than older ones, but considerable amounts were given to foragers. Drones behaved similarly. Between one-third and one-half of the distributed jelly was given to imagines; 10% and 16% of all workers received radioactive jelly from 100 nurses in the two colonies during one night. Thus, jelly is a very important food for adult honey bees. There was a remarkable exchange of label within the class of nurses themselves that is interpreted as communication within the social system.

Influence of diet, age and colony condition upon intestinal proteolytic activity and size of the hypopharyngeal glands in the honeybee (Apis mellifera L.)

Abstract Intestinal proteolytic activity, size of hypopharyngeal glands and dry weight of bees were investigated. Bees were either kept in cages (isolated or in groups) in an incubator, hived in small hives (200–300 individuals in three small combs) or in observation hives (about 2500 individuals in two combs). Artificial diets such as sucrose solution, sucrose with casein, sucrose with amino acids, honey, and honey with beebread were fed to the caged bees. Colony conditions such as the presence of brood and/or queen varied in the small hives. After emergence all bees, even those fed with sucrose solution, showed an increase in all parameters investigated. In all caged bees, except in those fed only sucrose, proteolytic activity increased at least till the 3rd day of life; the size of hypopharyngeal glands then decreased till the 8th day except in bees fed honey and beebread. In all bees that lived in small hives both these parameters increased at least till the 8th day and then were much lower and smaller in older bees that were already foragers respectively. The presence of a queen and unsealed brood neither influenced the intestinal proteolytic activity nor the size of the hypopharyngeal glands. In bees that lived in small hives these parameters developed in a similar manner to those of bees kept in observation hives. Bees fed for the first 3 days with merely a sucrose solution had low levels of proteolytic activities and small hypopharyngeal glands. If they were then put into a queenright observation hive till their 8th day, they could make up almost the entire deficiency.

Adaptation of hypopharyngeal gland development to the brood status of honeybee (Apis mellifera L.) colonies

We studied pollen consumption, head weight, hypopharyngeal gland (HPG) acini diameter, and protein synthesis and transfer in honeybee workers reared in colonies with normal and with decreasing amounts of brood. We found that head fresh weight is correlated with size of the glands and that pollen consumption is positively correlated with gland development. An effect of brood on size of the glands could be confirmed, but was not as profound as in previous studies. Similarly, no difference in the amount of protein synthesized or transferred in workers living under the two brood conditions was found. We suspect this is due to the fact that HPGs also supply food to young bees and in our study young bees were always present while in previous studies, colonies often lacked both brood and young bees.

Get in touch: cooperative decision making based on robot-to-robot collisions

We demonstrate the ability of a swarm of autonomous micro-robots to perform collective decision making in a dynamic environment. This decision making is an emergent property of decentralized self-organization, which results from executing a very simple bio-inspired algorithm. This algorithm allows the robotic swarm to choose from several distinct light sources in the environment and to aggregate in the area with the highest illuminance. Interestingly, these decisions are formed by the collective, although no information is exchanged by the robots. The only communicative act is the detection of robot-to-robot encounters. We studied the performance of the robotic swarm under four environmental conditions and investigated the dynamics of the aggregation behaviour as well as the flexibility and the robustness of the solutions. In summary, we can report that the tested robotic swarm showed two main characteristic features of swarm systems: it behaved flexible and the achieved solutions were very robust. This was achieved with limited individual sensor abilities and with low computational effort on each single robot in the swarm.

Drifting of honeybees

Summary: Drifting of honeybees depends on the arrangement, the colouring of the hives and on various environmental factors. Bees are able to distinguish between related and non-related individuals, so one aim of this study was to determine whether drifting also depends on relatedness. In addition we wanted to examine whether there are differences in survival of drifted bees and non-drifted bees and to model the component of alien worker bees in a colonys population.¶We used two non-related strains of bees. The colonies stood in rows. Each of the colonies had two non-related neighbour colonies, except for the colonies on the ends of the rows. From each colony, 200 newly emerged bees were marked individually and 100 of them were reintroduced into their original colony (native bees) and 100 into a non-related neighbouring colony (foreign bees). The marked bees were examined for presence on their 2nd, 6th, 9th, 16th, 25th and 34th day of life. Experiments were done in summer and fall. ¶There was no difference in survival and the amount of drifting of native and foreign bees. We also found no differences in the number of drifting bees for the two non-related strains. The bees never preferred related colonies when drifting. Bees of strain 1 did not show any preferences. In two experiments significantly more bees of strain 2 drifted into colonies of strain 1. Most bees drifted into the neighbouring colony next to the colony they left. In summer significantly more bees that had drifted until their 9th day of life, survived until the 25th day than bees that did not drift until that day. In fall we did not find this difference. This was true for bees of both strains. ¶Our data support the results of Jay (1965), who found that more bees drift from a centre colony to the end colonies of a row than vice versa. ¶With a model we calculated the component of alien worker bees living in a colonys population. On average, 22 ± 3% alien worker bees were calculated for edge and 42 ± 6% for inner hives in a row in our first experiment (summer). In a second experiment (fall) the components were 13 ± 1% for the edge colonies and 39 ± 4% for the inner colonies in the row. Drifting seems not to be influenced by relatedness and did not shorten the lifetime of the bees. This indicates a great tolerance against drifted bees and a high intermix of an apiarys population when no precautions to reduce drifting are taken.

Standard methods for artificial rearing of Apis mellifera larvae

Summary Originally, a method to rear worker honey bee larvae in vitro was introduced into the field of bee biology to analyse honey bee physiology and caste development. Recently, it has become an increasingly important method in bee pathology and toxicology. The in vitro method of rearing larvae is complex and can be developed as an art by itself, especially if the aim is to obtain queens or worker bees which, for example, can be re-introduced into the colony as able members. However, a more pragmatic approach to in vitro rearing of larvae is also possible and justified if the aim is to focus on certain pathogens or compounds to be tested. It is up to the researcher(s) to decide on the appropriate experimental establishment and design. This paper will help with this decision and provide guidelines on how to adjust the method of in vitro rearing according to the specific needs of the scientific project.

Trophallaxis within a robotic swarm: bio-inspired communication among robots in a swarm

Abstract This article presents a bio-inspired communication strategy for large-scale robotic swarms. The strategy is based purely on robot-to-robot interactions without any central unit of communication. Thus, the emerging swarm regulates itself in a purely self-organized way. The strategy is biologically inspired by the trophallactic behavior (mouth-to-mouth feedings) performed by social insects. We show how this strategy can be used in a collective foraging scenario and how the efficiency of this strategy can be shaped by evolutionary computation. Although the algorithm works stable enough that it can be easily parameterized by hand, we found that artificial evolution could further increase the efficiency of the swarm’s behavior. We investigated the suggested communication strategy by simulation of robotic swarms in several arena scenarios and studied the properties of some of the emergent collective decisions made by the robots. We found that our control algorithm led to a nonlinear, but graduated path selection of the emerging trail of loaded robots. They favored the shortest path, but not all robots converged to this trail, except in arena setups with extreme differences in the length of the two possible paths. Finally, we demonstrate how the flexibility of collective decisions that arise through this new strategy can be used in changing environments. We furthermore show the importance of a negative feedback in an environment with changing foraging targets. Such feedback loops allow outdated information to decay over time. We found that task efficiency is constrained by a lower and an upper boundary concerning the strength of this negative feedback.